The 1st Provisional Air Brigade was a temporary unit of the United States Army Air Service, commanded by Col. Billy Mitchell, operating out of Langley Field, Virginia, that was used in Project B to demonstrate the vulnerability of ships to aerial attack when, in July 1921, the "unsinkable" German dreadnought SMS Ostfriesland was sent to the bottom of the Atlantic Ocean by bombardment. Other targets included the German destroyer SMS G-102, the SMS Frankfurt, and the USS Iowa.